Submitted to: Agriculture Ecosystems and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2013
Publication Date: 3/30/2013
Citation: Franzluebbers, A.J., Seman, D.H., Stuedemann, J.A. 2013. Forage dynamics in mixed tall fescue-bermudagras pastures of the Southern Piedmont USA. Agriculture Ecosystems and the Environment. 168:37-45. Interpretive Summary: Development of perennial pastures composed of both cool- and warm-season grasses in the southern region would help achieve high productivity of year-round grazing systems and help avoid the high costs of cutting and making hay. How bermudagrass pastures can be manipulated to support introduction and maintenance of tall fescue stand in a balanced mixture has not been adequately established in the scientific literature. Scientists with the USDA Agricultural Research Service in Watkinsville Georgia conducted a multi-year investigation of interseeding Georgia-5 tall fescue with wild endophyte infection into Coastal bermudagrass pastures in the Piedmont of Georgia. Pastures were managed with three different fertilization regimes (inorganic only, organic + inorganic, and organic only) and four different utilization strategies (unharvested, low and high grazing pressure, and hayed) for 7 years after introduction of tall fescue. Introduction of tall fescue into Coastal bermudagrass sod was successful in developing a mixed tall fescue-bermudagrass pasture system capable of greatly expanded grazing opportunities throughout the year. Days of grazing were increased from 140 days on bermudagrass pasture only to ~260 days on tall fescue-bermudagrass pasture. It appears that careful management of the wild-endophyte-infected tall fescue component is most critical in determining the balance of tall fescue and bermudagrass components, because of its tolerance to high grazing pressure from one perspective and its dominance over bermudagrass through smothering from another perspective. Broiler litter application did promote greater production of forage for hay harvest, but not for grazing. Balanced tall fescue and bermudagrass components occurred with either stocker grazing regimes, but dominance of the sward with tall fescue when forage was left unharvested for conservation or removed continuously with hay harvest. We conclude that mixed tall fescue-bermudagrass pastures grazed by cattle produced nearly equivalent total forage production as from separate pastures, but from half the land area. This production perspective needs to be balanced against the results of environmental analyses, which will be reported elsewhere.
Technical Abstract: Botanical composition and forage productivity of mixed cool- and warm-season perennial pastures are important determinants of agricultural sustainability that can be influenced by management. We evaluated the factorial combination of three sources of nutrient application (inorganic only, organic + inorganic combination, and organic only) and four forage utilization regimes (unharvested, low and high grazing pressure, and hayed) on botanical composition, residual forage mass, and forage production during 7 yr of management [tall fescue (Lolium arundinaceum) overseeded into existing bermudagrass (Cynodon dactylon) sod] in Georgia. Nutrient source had few major impacts on responses, except for greater hay yield with organic fertilization (broiler litter) than with organic + inorganic and inorganic only fertilization. Botanical composition of grazed pastures shifted with time from initial dominance with bermudagrass (~50% basal area) to mixed composition of tall fescue (60%)/bermudagrass (36%) under low grazing pressure and tall fescue (45%)/bermudagrass (48%) under high grazing pressure. To maintain optimum botanical composition and productivity for year-round grazing, forage mass needs to be balanced within a maximum threshold to avoid deterioration of forage quality and a minimum threshold to avoid environmental degradation. These multi-year results will help producers in warm, moist climates develop more sustainable grazing systems.